The proposed project is to study the hemodynamic effects of one kidney renal hypertension upon pregnant sheep. The major emphasis is upon the changes in uteroplacental blood flow and vascular resistance. Pregnant sheep are chronically instrumented at about 80 gestational days for determination of arterial pressure and uteroplacental blood flow by electromagnetic flow transducers. Uterine venous catheters are also placed so that blood samples may be analyzed for plasma renin activity and Prostaglandin E concentration. Following three weeks of recovery and collection of baseline data, renal hypertension is induced by renal artery constriction and contralateral nephrectomy. The animals are then monitored until term. In another group of animals cardiac output and blood volume will be studied. BIBLIOGRAPHIC REFERENCES: Woods, J. R. Jr., Brinkman, C.R. III, Dandavino, A., Murayama, K. and Assali, N.S.: Action of histamine and H1 and H2 blockers on the cardiopulmonary circulation, Am. J. Physiol., 232/1, H73-78, 1977. Dandavino, A., Woods, J.R. Jr., Nuwayhid, B., Brinkman, C.R.III, Blanchard, K., Clark, K.E., and Assali, N.S.: Cardiovascular reactivity of sheep to autonomic stimuli during adrenergic depletion. Gynecol. Investiga., 8:38, 1977. (abstract).